1. Field of the Invention
The present invention generally relates to an ATM exchange system and, more particularly, to a method and apparatus for setting a signaling virtual channel used for signal transmission in an ATM exchange system.
2. Description of the Related Art
A conventional asynchronous transfer mode (ATM) exchange system establishes or cancels a communication channel for transferring communication information received from a subscriber terminal in accordance with signaling information which is provided to setup a call. The ATM exchange receives the signal information from the subscriber terminal through a signaling virtual channel (SVC). The signaling virtual channel (SVC) is fixedly established so that the signaling information can be transmitted any time.
In the conventional ATM exchange system, a virtual path identifier (VPI) and a virtual channel identifier (VCI) are registered for setting the signaling virtual channel (SVC). The virtual path identifier (VPI) and a virtual channel identifier (VCI) are assigned to each subscriber terminal so that the signaling virtual channel (SVC) can be established by assigning a transmission bandwidth for transmitting the signaling information to each pair of the virtual path identifier (VPI) and the virtual channel identifier (VCI).
Accordingly, the signaling virtual channel (SVC) is continuously established on the communication path irrespective of presence of a communication call so that a subscriber can send a call setup request (a request for establishing a communication path for transferring communication information) or a call disconnect request (a request for disconnecting the communication path) through the signaling virtual channel (SVC).
Accordingly, the signaling virtual channel (SVC) is maintained even after the communication channel is established in which condition the signal virtual channel (SVC) is not needed. That is, the bandwidth used for the signaling virtual channel (SVC) is continuously reserved despite that the signaling virtual channel (SVC) is not necessary after the establishment of the communication channel is completed. Accordingly, the bandwidth assigned to the signaling virtual channel (SVC) cannot be assigned to the communication channel for transmitting communication information. Thus, the entire bandwidth allocated to the communication path of the ATM exchange system cannot be effectively used for the communication channel which is established for transmitting the communication information other than the signaling information.
Additionally, since the signaling virtual channel (SVC) must be identified by a previously registered virtual path identifier (VPI) and a virtual channel identifier (VCI), a subscriber terminal must send a call setup request upon recognition of the virtual path identifier (VPI) and the virtual channel identifier (VCI) provided in the ATM exchange system to which the subscriber terminal is to be connected.
Accordingly, a subscriber using a portable communication terminal must transmit the signaling information by using different signaling virtual path identifier (VPI) and the virtual channel identifier (VCI) for each ATM exchange system. Thus, a call setup request procedure is complicated and inconvenient.
It is a general object of the present invention to provide an improved and useful method and apparatus for establishing a signaling virtual channel for an ATM exchange system in which the above-mentioned problems are eliminated.
A more specific object of the present invention is to provide a method and apparatus for establishing a signaling virtual channel for an ATM exchange system to establish a signaling virtual channel (SVC) only when it is necessary so that a bandwidth conventionally reserved for a signaling channel for transmitting signaling information is used for transmitting communication information.
Another object of the present invention is to provide a method and apparatus for establishing a signaling virtual channel for an ATM exchange system which method and apparatus permit a subscriber terminal which is for a different ATM exchange system enabling signaling information to be transmitted or received without recognizing specific values of the signaling virtual path identifier (VPI) and the virtual channel identifier (VCI) registered for each ATM exchange system.
In order to achieve the above mentioned objects, there is provided according to one aspect of the present invention a method for setting a signaling virtual channel (SVC) between a subscriber terminal and an asynchronous transfer mode (ATM) exchange system, the signaling virtual channel (SVC) being identified by a virtual path identifier (VPI) and a virtual channel identifier (VCI) for signaling, the method comprising the steps of:
establishing the signaling virtual channel (SVC) between the subscriber terminal and the asynchronous transfer mode exchange system by selecting the virtual path identifier (VPI) and the virtual channel identifier (VCI) for signaling only when a request for a call connection is made by the subscriber terminal or only when a notification of reception of a call is sent to the subscriber terminal;
establishing a communication path between the subscriber terminal and the asynchronous transfer mode exchange system for transmitting communication information by transmitting communication call setting information through the signaling virtual channel (SVC); and
releasing the signaling virtual channel (SVC) after an establishing operation of the communication path is completed.
According to the above-mentioned invention, the signaling virtual channel (SVC) is established only when a request for connecting a call is made. After the communication path is established by using the communication call setting information transmitted through the signaling virtual channel (SVC), the signaling virtual channel is released since there is no need to maintain the signaling virtual channel (SVC). Accordingly, a bandwidth used for establishing the signaling virtual channel can be used for establishing a communication path for transmitting communication information. Thus, the entire bandwidth can be effectively used for establishing the communication path.
In method according to this invention, the step of establishing the signaling virtual channel may include:
selecting a virtual path identifier (VPI) and a virtual channel identifier (VCI) for signaling which are assumed to be usable for both the subscriber terminal and the asynchronous transfer mode (ATM) exchange system;
selecting a different virtual path identifier (VPI) and a different virtual channel identifier (VCI) for signaling when the selected virtual path identifier (VPI) and virtual channel identifier (VCI) are unusable for at least one of the subscriber terminal and the asynchronous transfer mode exchange system; and
repeating the step of selecting a virtual path identifier (VPI) and a virtual channel identifier (VCI) and the step of selecting a different virtual path identifier (VPI) and a different virtual channel identifier (VCI) until virtual path identifier (VPI) and the different virtual channel identifier (VCI) usable for both the subscriber terminal and the asynchronous transfer mode (ATM) exchange system are selected.
In this invention, selection of the virtual path identifier (VPI) and the virtual channel identifier (VCI) are repeated until the virtual path identifier (VPI) and the virtual channel identifier (VCI) usable for both the subscriber terminal and the asynchronous transfer mode exchange system are finally selected. Thus, a possibility of failure of establishing the signaling virtual channel (SVC) which results in a discommunicable state is reduced.
The method according to the present invention may further comprise the step of disconnecting the communication path when a predetermined communication period has been elapsed after the signaling virtual channel (SVC) is released.
According to this invention, the communication path can be disconnected without following a normal signaling procedure using the signaling virtual channel (SVC) by monitoring the predetermined communication period. Thereby, the signaling virtual channel (SVC) can be released when communication is being performed through the communication path. Thus, a bandwidth assigned to the signaling virtual channel (SVC) can be effectively used for the communication path.
Additionally, the method according to the present invention may further comprise the step of disconnecting the communication path when a communication requesting period has been elapsed after the signaling virtual channel (SVC) is released, information regarding the communication requesting period being included in the communication call setting information.
According to this invention, the communication path can be disconnected without following a normal signaling procedure using the signaling virtual channel (SVC) by monitoring the requested communication period. Thereby, the signaling virtual channel (SVC) can be released when communication is being performed through the communication path. Thus, a bandwidth assigned to the signaling virtual channel (SVC) can be effectively used for the communication path.
Further, the method according to the present invention may further comprise the step of disconnecting the communication path when a communication failure is detected in the asynchronous transfer mode (ATM) exchange system.
According to this invention, the communication path can be disconnected without following a normal signaling procedure using the signaling virtual channel (SVC) by monitoring a failure occurring in the asynchronous transfer mode exchange system. Thereby, the signaling virtual channel (SVC) can be released when communication is being performed through the communication path. Thus, a bandwidth assigned to the signaling virtual channel (SVC) can be effectively used for the communication path.
Additionally, there is provided according to another aspect of the present invention an apparatus for setting a signaling virtual channel (SVC) between a subscriber terminal and an asynchronous transfer mode (ATM) exchange system, the signaling virtual channel (SVC) being identified by a virtual path identifier (VPI) and a virtual channel identifier (VCI) for signaling, a communication path being established between the subscriber terminal and the asynchronous transfer mode (ATM) exchange system by exchanging communication call setting information through the signaling virtual channel (SVC), the apparatus comprising:
a signal management unit receiving a signal transmitted from the subscriber terminal when a request for connecting a call is made by the subscriber terminal, the signal including the virtual path identifier (VPI) and the virtual channel identifier (VCI) for signaling;
a bandwidth management unit determining whether or not the virtual path identifier (VPI) and the virtual channel identifier (VCI) included in the signal received by the signal management unit are usable for signaling so as to acquire the signaling virtual channel (SVC) when the virtual path identifier (VPI) and the virtual channel identifier (VCI) are usable for signaling; and
a signaling virtual channel (SVC) protocol control unit selecting the virtual path identifier (VPI) and the virtual channel identifier (VCI) for signaling, when a notification of reception of a call is sent to the subscriber terminal, so as to inquire the bandwidth management unit whether or not the selected virtual path identifier (VPI) and the selected virtual channel identifier (VCI) are usable for signaling so that an instruction to transmit the selected virtual path identifier (VPI) and the selected virtual channel identifier (VCI) is sent to the subscriber terminal receiving a call, the signaling virtual channel (SVC) protocol control unit instructing a disconnection of the signaling virtual channel (SVC) after a setting operation of the communication path to the subscriber terminal is completed.
Additionally, the apparatus according to the present invention, the signaling virtual channel (SVC) protocol control unit may select a virtual path identifier (VPI) and a virtual channel identifier (VCI) for signaling which are assumed to be usable for both the subscriber terminal and the asynchronous transfer mode (ATM) exchange system when a notification of reception of a call is sent to the subscriber terminal;
the signaling virtual channel (SVC) protocol control unit may also select a different virtual path identifier (VPI) and a different virtual channel identifier (VCI) for signaling when the selected virtual path identifier (VPI) and virtual channel identifier (VCI) are unusable for at least one of the subscriber terminal and the asynchronous transfer mode exchange system; and
the signaling virtual channel (SVC) protocol control unit may repeat the selection of a virtual path identifier (VPI) and a virtual channel identifier (VCI) and the selection of a different virtual path identifier (VPI) and a different virtual channel identifier (VCI) until virtual path identifier (VPI) and the different virtual channel identifier (VCI) usable for both the subscriber terminal and the asynchronous transfer mode (ATM) exchange system are selected.
Further, in the apparatus according to the present invention, the signaling virtual channel (SVC) protocol control unit may send an instruction to disconnect the communication path when a predetermined communication period has been elapsed after the signaling virtual channel (SVC) is released.
Alternatively, the signaling virtual channel protocol (SVC) control unit may send an instruction to disconnect the communication path when a communication requesting period has been elapsed after the signaling virtual channel (SVC) is released, information regarding the communication requesting period being included in the communication call setting information.
Further, the signaling virtual channel (SVC) protocol control unit may send an instruction to disconnect the communication path when a communication failure is detected in the asynchronous transfer mode (ATM) exchange system.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the following detailed information.